Multicarrier-based data transmission method and apparatus in mobile communication system

ABSTRACT

A multicarrier-based data transmission method and an apparatus for use in a mobile communication system are provided. A Radio Network Temporary Identity (RNTI) reception method of a terminal in a wireless communication system supporting inter-evolved Node B (eNB) carrier aggregation includes receiving cell information on at least one activated cell under control of an eNB, configuring first and second RNTIs allocated by the eNB, monitoring the at least one activated cell for the first RNTI, and monitoring a primary cell among the at least one activated cell for the second RNTI.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/989,896 filed on May 25, 2015, which issued as U.S. Pat. No.10,601,555 on Mar. 24, 2020, which is a continuation application ofprior application Ser. No. 14/608,589, filed on Jan. 29, 2015, whichissued as U.S. Pat. No. 9,985,756 on May 29, 2018, which was based onand claimed priority under 35 U.S.C. § 119(a) of Korean patentapplications numbers 10-2014-0011266, 10-2014-0038833, 10-2014-0133366,10-2014-0143643, and 10-2014-0160369, filed on Jan. 29, 2014, Apr. 1,2014, Oct. 2, 2014, Oct. 22, 2014, and Nov. 17, 2014, respectively, inthe Korean Intellectual Property Office, the disclosure of each of whichis incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to a mobile communication system. Moreparticularly, the present disclosure relates to a multicarrier-baseddata transmission method and an apparatus for use in the mobilecommunication system.

BACKGROUND

Mobile communication systems were developed to provide mobile users withcommunication services. With rapid technological advancements, themobile communication systems have evolved to the level capable ofproviding high speed data communication service beyond the earlyvoice-oriented services.

Recently, standardization for a Long Term Evolution (LTE) system, as oneof the next-generation mobile communication systems, is underway in the3^(rd) Generation Partnership Project (3GPP). LTE is a technology forrealizing high-speed packet-based communications with the data rate ofup to 100 Mbps, which is higher than the currently available data rate,and its standardization is almost complete.

Recent studies are focused on the LTE-Advanced (LTE-A) for improvingdata rate with the adoption of various new techniques to legacy LTEsystem. One of such technologies is Carrier Aggregation. CarrierAggregation is a technology allowing a terminal to use multiple downlinkcarriers and multiple uplink carriers unlike the technology of therelated art of using one downlink carrier and one uplink carrier fordata communication.

The current release of LTE-A specifies only an intra-evolved Node B(eNB) carrier aggregation. This diminishes the applicability of carrieraggregation function and is likely to cause carrier aggregation failureespecially in a scenario where a plurality of pico cells and one macrocell coexist.

Therefore, a need exists for a method and an apparatus for facilitatinginter-eNB carrier aggregation.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and an apparatus for facilitatinginter-evolved Node B (eNB) carrier aggregation.

In accordance with an aspect of the present disclosure, a Radio NetworkTemporary Identity (RNTI) reception method of a terminal in a wirelesscommunication system supporting inter-evolved Node B (eNB) carrieraggregation is provided. The method includes receiving cell informationon at least one activated cell under control of an eNB, configuringfirst and second RNTIs allocated by the eNB, monitoring the at least oneactivated cell for the first RNTI, and monitoring a primary cell amongthe at least one activated cell for the second RNTI.

In accordance with another aspect of the present disclosure, a terminalfor receiving Radio Network Temporary Identity (RNTI) in a wirelesscommunication system supporting inter-evolved Node B (eNB) carrieraggregation is provided. The terminal includes a transceiver configuredto transmit and receive signals to and from an eNB and a controllerconfigured to receive cell information on at least one activated cellunder control of an eNB, to configure first and second RNTIs allocatedby the eNB, to monitor the at least one activated cell for the firstRNTI, and to monitor a primary cell among the at least one activatedcell for the second RNTI.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram illustrating a Long Term Evolution (LTE) systemarchitecture according to various embodiments of the present disclosure;

FIG. 2 is a diagram illustrating a protocol stack of an LTE systemaccording to various embodiments of the present disclosure;

FIG. 3 is a diagram illustrating an intra-evolved Node B (eNB) carrieraggregation for a User Equipment (UE) according to an embodiment of thepresent disclosure;

FIG. 4 is a diagram illustrating an inter-eNB carrier aggregationaccording to an embodiment of the present disclosure;

FIG. 5 is a diagram illustrating a macro cell uplink and a pico celluplink according to an embodiment of the present disclosure;

FIG. 6 is a diagram illustrating an uplink transmit power adjustmentscheme according to an embodiment of the present disclosure;

FIG. 7 is a flowchart illustrating an uplink transmit power controlprocedure of a UE according to an embodiment of the present disclosure;

FIG. 8 is a flowchart illustrating an uplink transmit power controlprocedure of a UE according to an embodiment of the present disclosure;

FIG. 9 is a diagram illustrating a situation where two uplink subframesare not aligned according to an embodiment of the present disclosure;

FIG. 10 is a signal flow diagram illustrating a signal processingprocedure for transmitting signals using multiple carriers at a UE in amobile communication system according to an embodiment of the presentdisclosure;

FIG. 11 is a block diagram illustrating a configuration of a UEaccording to an embodiment of the present disclosure;

FIG. 12 is a block diagram illustrating a configuration of an eNBaccording to an embodiment of the present disclosure;

FIG. 13 is a flowchart illustrating an uplink transmit power controlprocedure of a UE according to an embodiment of the present disclosure;

FIG. 14 is a flowchart illustrating a procedure of determining, at a UE,a serving cell to be monitored for receiving Radio Network TemporaryIdentity (RNTI) according to an embodiment of the present disclosure;

FIG. 15 is a diagram illustrating an operation mechanism of a UE withtwo Medium Access Control (MAC) entities according to an embodiment ofthe present disclosure;

FIG. 16 is a flowchart illustrating a MAC procedure of a UE according toan embodiment of the present disclosure;

FIG. 17 is a flowchart illustrating a Secondary Serving cell (SCell)release procedure of a UE according to an embodiment of the presentdisclosure;

FIG. 18 is a flowchart illustrating an SCell management procedure of aUE in RLF situation according to an embodiment of the presentdisclosure; and

FIG. 19 is a signal flow diagram illustrating an in-device interferencecontrol procedure of a UE according to an embodiment of the presentdisclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

FIG. 1 is a diagram illustrating a Long Term Evolution (LTE) systemarchitecture according to various embodiments of the present disclosure.

Referring to FIG. 1, the radio access network of the mobilecommunication system includes evolved Node Bs (eNBs) 105, 110, 115, and120, a Mobility Management Entity (MME) 125, and a Serving-Gateway(S-GW) 130. The term ‘eNB’ is used interchangeably with terms ‘node B’and ‘base station.’ The User Equipment (hereinafter, referred to as UE)135 connects to an external network via eNBs 105, 110, 115, and 120 andthe S-GW 130.

Referring to FIG. 1, the eNBs 105, 110, 115, and 120 correspond to thelegacy node Bs of the UMTS system. The eNBs allow the UE 135 toestablish a radio channel and are responsible for complicated functionsas compared to the legacy node B. In the LTE system, all the usertraffic including real time services, such as Voice over InternetProtocol (VoIP), is provided through a shared channel and thus there isa need of a device which is located in the eNB to schedule data based onthe state information, such as buffer states, power headroom states,channel states of the UEs, and the like.

Typically, one eNB controls a plurality of cells. In order to secure thedata rate of up to 100 Mbps, the LTE system adopts Orthogonal FrequencyDivision Multiplexing (OFDM) as a radio access technology. In addition,the LTE system adopts Adaptive Modulation and Coding (AMC) to determinethe modulation scheme and channel coding rate in adaptation to thechannel condition of the UE.

The S-GW 130 is an entity to provide data bearers so as to establish andrelease data bearers under the control of the MME 125. The MME 125 isresponsible for UE mobility management and other control functions andmay be connected to a plurality of eNBs.

FIG. 2 is a diagram illustrating a protocol stack of an LTE systemaccording to various embodiments of the present disclosure.

Referring to FIG. 2, the protocol stack of the LTE system includesPacket Data Convergence Protocol (PDCP) 205 and 240, Radio Link Control(RLC) 210 and 235, Medium Access Control (MAC) 215 and 230, and Physical(PHY) 220 and 225.

The PDCP 205 and 240 is responsible for IP headercompression/decompression, and the RLC 210 and 235 is responsible forsegmenting the PDCP Protocol Data Unit (PDU) into segments inappropriate size for Automatic Repeat Request (ARQ) operation. The MAC215 and 230 is responsible for establishing connection to a plurality ofRLC entities so as to multiplex the RLC PDUs into MAC PDUs anddemultiplex the MAC PDUs into RLC PDUs. The PHY 220 and 225 performschannel coding on the MAC PDU and modulates the MAC PDU into OFDMsymbols to transmit over radio channel or performs demodulating andchannel-decoding on the received OFDM symbols and delivers the decodeddata to the higher layer.

FIG. 3 is a diagram illustrating an intra-eNB carrier aggregation for aUE according to an embodiment of the present disclosure.

Referring to FIG. 3, an eNB transmits and receives signals throughmultiple carriers across a plurality of frequency bands. For example, aneNB 305 can be configured to use the carrier 315 with center frequencyf1 and the carrier 310 with center frequency f3. If carrier aggregationis not supported, a UE 330 has to transmit/receive data using one of thecarriers 310 and 315. However, the UE 330 having the carrier aggregationcapability can transmit/receive data using both the carriers 310 and315. The eNB can increase the amount of the resource to be allocated tothe UE having the carrier aggregation capability in adaptation to thechannel condition of the UE so as to improve the data rate of the UE330. This approach of aggregating the downlink carriers transmitted byor uplink carriers received by an eNB is referred to as inter-eNBcarrier aggregation. However, there may be a situation requiring anapproach of aggregating the downlink carriers transmitted by differenteNBs or the uplink carriers received by different eNBs unlike thesituation of FIG. 3.

FIG. 4 is a diagram illustrating an inter-eNB carrier aggregationaccording to an embodiment of the present disclosure.

Referring to FIG. 4, assuming that an eNB 1 405 operates a carrier withthe center frequency at f1 and an eNB 2 415 a carrier with the centerfrequency at f2, if a UE 430 aggregates the carrier with the downlinkcenter frequency at f1 and the carrier with the downlink centerfrequency at f12, i.e., one UE 430 aggregates the carriers of twodifferent eNBs, and this is referred to as inter-eNB Carrier Aggregation(CA) in an embodiment of the present disclosure. In the followingdescription, the term ‘Dual Connectivity (DC)’ is used interchangeablywith the term ‘inter-eNB CA’. For example, if DC is configured, thisindicates that the inter-eNB CA is configured.

The following definitions are provided to facilitate understanding ofcertain terms used frequently herein.

Assuming that a cell is configured with one downlink carrier and oneuplink carrier of an eNB in a concept of the related art, the carrieraggregation can be understood as if the UE communicates data viamultiple cells. At this time, the peak data rate and the number ofaggregated carriers have positive correlation.

In the following description, if a UE receives data through a certaindownlink carrier or transmits data through a certain uplink carrier,this indicates that the UE transmits/receives data through a controlchannel and a data channel provided by the cell corresponding to thecenter frequency and frequency band characterizing the carrier. In thefollowing description, the carrier aggregation can be expressed likethis ‘a plurality of serving cells are configured’ along with the use ofthe terms ‘Primary Serving cell (PCell),’ ‘Secondary Serving cell(SCell),’ ‘activated service cell,’ and the like. These terms are usedin the same meaning as those used in the LTE mobile communicationsystem. In following description, the terms ‘carrier,’ ‘componentcarrier,’ and ‘serving cell’ are used interchangeably in the samemeaning.

In the following description, a set of the serving cells controlled byone eNB is referred to as a Cell Group or Carrier Group (CG). A cellgroup is classified into one of Master Cell Group (MCG) and SecondaryCell Group (SCG). The MCG denotes a set of the serving cell controlledby an eNB controlling the PCell (hereinafter, referred to as Master eNB(MeNB), and the SCG denotes a set of the serving cells controlled by theeNB which does not control the PCell, i.e., the eNB which controlsSCells (hereinafter, referred to as Slave eNB (SeNB). The eNB notifiesthe UE whether a serving cell belongs to the MCG or SCG in the procedureof configure the corresponding serving cell. A UE may be configured withone MCG and one or more SCGs. Although the description is directed tothe case where one SCG is configured for convenience purpose, thesubject matter of the present disclosure can be applied, withoutmodification, to the case where more than one SCG are configured. ThePCell and SCell are terms expressing the types of the serving cellconfigured to the UE. The PCell and SCell are different in that thePCell remains in the activated state while the SCell transitions betweenthe activated state and the deactivated state repeatedly according tothe command of the eNB. The UE mobility is controls mainly inassociation with the PCell, and the SCell may be understood as an extraserving cell for data communication. In the following description, theterms ‘PCell’ and ‘SCell’ are used in the same meaning as those definedin the LTE standards TS36.331 and TS 36.321.

The present disclosure is directed to the network in which the macro andpico cells coexist. The macro cell is the cell controlled by a macro eNBand has a relatively large service coverage area. In contrast, the picocell is the cell controlled by the SeNB and has a small service coveragearea as compared to the macro cell. Although there is no strictcriterion for distinguishing between the macro and pico cells, it isassumed that the macro cell has a radius about 500 m while the pico cellhas a radius about a few meters. In the following description, the terms‘pico cell’ and ‘small cell’ are used interchangeably.

Referring to FIG. 4, if the eNB 1 405 is the MeNB and the eNB 2 415 isthe SeNB, a serving cell 410 having the center frequency at f1 is theserving cell belonging to the MCG, and a serving cell 420 having thecenter frequency at f2 is the serving cell belonging to the SCG.

In the following description, other terms may be used interchangeablywith MCG and SCG to help understanding. For example, the terms ‘primaryset’ and ‘secondary set’ and ‘primary carrier group’ and ‘secondarycarrier group’ may be used interchangeably. However, it is noted thatthey are different in spelling but the same in meaning. The main purposeof these terms is to clarify which cell is under the control of the eNBcontrolling the PCell of a specific UE, and the UE and the correspondingcell may operate differently depending on whether the corresponding cellis controlled by the eNB controlling the PCell of the specific UE.

Although the UE may be configured with one or more SCGs, the followingdescription is directed to the case where one SCG is configured forexplanation convenience. The SCG may include a plurality of SCells ofwhich one has a special attribute.

In the intra-eNB CA, the UE transmits the HARQ feedback and CSI for theSCell(s) as well as the HARQ feedback and CSI for the PCell through thePCell PUCCH. This is to apply the CA to the UE having no simultaneousuplink transmission capability.

In the inter-eNB CA, it may be impossible to transmit the HARQ feedbackand CSI of the SCG SCells on the PCell PUCCH. This is because althoughthe HARQ feedback has to be delivered within the HARQ Round Trip Time(RTT) (typically 8 ms) the transmission delay between the MeNB and SeNBmay be longer than the HARQ RTT.

In order to address this issue, PUCCH transmission resource isconfigured to one of the SCG SCells to transmit the HARQ feedback andCSI for the SCG SCells. This special SCell is referred to as primarySCell (pSCell).

Since the MeNB and SeNB perform scheduling independently, the uplinktransmission in the MCG and the uplink transmission in the SCG may beoverlapped in the time domain. Since the uplink transmit power of the UEis limited, if the required transmit power is greater than the maximumallowed transmit power, the UE performs uplink transmission at a loweredtransmit power level, resulting in degradation of uplink transmissionquality.

If a scheduler performs uplink scheduling of the UE, the scheduler hasto monitor to avoid the transmit power shortage as far as possible. Inthe inter-eNB CA, however, two schedulers perform schedulingindependently it is difficult to rule out the occurrence of transmitpower shortage situation.

The present disclosure proposes a method and an apparatus for minimizingthe uplink transmission quality degradation when the transmit powershortage situation occurs in the inter-eNB CA mode.

FIG. 5 is a diagram illustrating a macro cell uplink and a pico celluplink according to an embodiment of the present disclosure.

There may be a difference between the uplink transmit powers of thesmall and macro cells for the following reasons.

-   -   The probability of no existence of obstacle between the UE and        the small cell receiver is noticeably higher than the        probability of no obstacle between the UE and the macro cell        receiver.    -   It is likely that the distance between the UE and the small cell        receiver is shorter than the distance between the UE and the        macro cell receiver.

If a transmission/reception device in the range of line of sight, thisindicates that the communication quality is good as compared to theopposite situation and thus it is possible to reduce the transmit powerlevel. The shorter the distance between the transmitter and thereceiver, the less the pathloss and the lower the transmit power.

Referring to FIG. 5, assuming that the distance between a UE 510 and anMeNB 505 is 250 m and the distance between the UE 510 and an SeNB 515 is20 m, a pathloss 520 between the UE 510 and the MeNB 505 is 118.4 dB anda path loss 525 between the UE 510 and the SeNB 515 is 64.0 db. Forexample, the difference between the uplink signal strengths between theMeNB 505 and the SeNB 515 is 54.4 (about 275400 fold). Since thetransmit power required to the UE increases as the pathloss to the eNBincreases, the required transmit power of the UE for the MeNB 505 isgreater noticeably than the required transmit power of the UE for theSeNB 515.

If the total required transmit power for the MeNB and SeNB is greaterthan the maximum allowed transmit power of the UE, the UE may performthe equal power scaling on the transmit powers for the two eNBs. If therequired transmit power difference is noticeable between the MeNB andSeNB, the equal power scaling affects significantly worse influence tothe transmission quality of the downlink of the low required transmitpower.

For example, if a 336-bit VoIP packet is transmitted in the macro celland a 36696-bit packet is transmitted in the small cell and if thedistance between the UE and the MeNB is 500 m and the distance betweenthe UE and the SeNB is 50 and if a Transmission Power Control (TPC) forincreasing the transmit power as much as 3 dB is received, the requiredtransmit powers for the MeNB (macro cell) and the SeNB (small cell) aredetermined as shown in Table 1.

TABLE 1 Macro cell-required Tx power 26.96 dBm/497.04 mW Smallcell-required Tx power −7.65 dBm/0.17 mW 

Assuming that the maximum allowed transmit power of the UE is 20 dBm, ifthe equal power scaling is applied, the two transmit powers aredetermined as shown in Table 2.

TABLE 2 macro cell Tx power 20.0 dBm/ Transmission quality degradationof 99.97 mW same strength (6.96 dB) occurs in both the macro and smallcell transmissions. small cell Tx power −14.6 dBm/ 0.03 mW

Meanwhile, if only the highest required transmission power is reducedwhile the lowest required transmit power is maintained (i.e.,differential power scaling), the transmit powers are determined as shownin Table 3.

TABLE 3 macro cell Tx power 19.99 dBm/ Transmission quality degradationof 99.83 mW 6.97 db occurs in macro cell transmission. No transmissionquality degradation occurs in small cell transmission. small cell Txpower −7.65 dBm/ 0.17 mW

As shown in the tables, when the required transmit power difference issignificant, if the transmit power of the uplink of which requiredtransmit power is very low is reduced, the total transmit power isaffected little. However, if the transmit power of the uplink of whichrequired transmit power is low is reduced, the transmission quality ofthe corresponding uplink degrades significantly. Accordingly, it isadvantageous to decrease the transmit power of the uplink with the highrequired transmit power while maintain the transmit power of the uplinkwith the low required transmit power in view of the total transmissionquality.

In the case that the UE operates in the macro cell, such an extremetransmit power inequality does not occurs. In the case that the UEperforms uplink transmission in the macro and small cellssimultaneously, such an extreme transmit power inequality is likely tooccur.

As described above, one SCG may be configured with plural SCells and oneMCG with plural serving cells. In the PCell and pSCell, the PUCCH andPUSCH may be transmitted simultaneously. For the case that various typesof uplink channels are transmitted through a plurality of serving cellsof multiple cell groups as above, the present disclosure proposes a2-operation priority determination method for determining the prioritiesamong the cells groups first and then the priorities among uplinks inthe cell group. The 2-operation priority determination method of thepresent disclosure applies the differential power scaling rather thanthe equal power scaling for the same types of uplink transmissionsaccording to the cell group.

FIG. 6 is a diagram illustrating an uplink transmit power adjustmentscheme according to an embodiment of the present disclosure.

Referring to FIG. 6, it is assumed that uplink transmission is performedat a subframe in a serving cell of the MCG.

-   -   PUCCH transmission is performed in a PCell at operation 605,    -   PUSCH transmission is performed in one MCG serving cell at        operation 610, and    -   PUSCH transmission is performed in another MCG serving cell at        operation 615.

In the embodiment of FIG. 6, it is also assumed that uplink transmissionis performed at a subframe which is overlapped with the above subframein whole or in part in an SCG serving cell.

-   -   PUCCH transmission is performed in a pSCell at operation 620,    -   PUSCH transmission is performed in one SCG SCell at operation        625, and    -   PUSCH transmission is performed in another SCG SCell at        operation 630.

The UE determines the required transmit powers for the uplinktransmissions. Referring to FIG. 6, the heights of the arrowsrepresenting the respective uplink transmission indicate the requiredtransmit power levels of the respective uplink transmissions.

If the sum of the required transmit powers of the uplink transmissionsis greater than the maximum allowed transmit power of the UE, the UEdetermines the priorities among the respective uplink transmissions indifferent operations to select the uplink transmission power to bereduced with priority.

The UE allocates priorities to the cell groups at the first operationand then determines the priorities among the uplink transmissions percell group at the second operation. The UE reduces the transmit power ofthe uplink transmission with the low priority.

The UE may allocate priorities to the cell groups using one of thefollowing methods.

Cell Group Priority Determination Method 1

The UE allocates to a cell group (e.g., an MCG) a priority higher thanthose of other cell groups.

In this case, since the important messages, such as RRC controlmessages, are transmitted through the MCG, it is preferred to allocate ahigh priority for MCG transmission.

Cell Group Priority Determination Method 2

The UE compares the sums of uplink required transmit powers of the cellgroups and allocates a low priority to the cell group with the highestsum of the transmit powers and a high priority to the cell group withthe lowest sum of the transmit powers.

For example, the sum of the required transmit powers in MCG correspondsto the sum of the required transmit powers of the uplink transmissions605, 610, and 615, and the sum of the required transmit powers in SCGcorresponds to the sum of the required transmit powers of the uplinktransmissions 620, 625, and 630. Referring to FIG. 6, since the sum ofthe required transmit powers in MCG is greater than the sum of therequired transmit powers in SCG, the UE allocates to the MCG a lowpriority.

As described above, it is advantageous to decrease the transmit power ofthe uplink with the high required transmit power rather than to decreasethe transmit power of the uplink with the low required transmit power inview of the total transmission quality. Accordingly, it is preferred forthe UE to allocate the low priority to the cell group with the highrequired transmit powers sum to reduce the transmit power with priority.

Cell Group Priority Determination Method 3

If the difference (or ratio) between the sums of uplink requiredtransmit powers of the respective cell groups is equal to or greaterthan a certain threshold, the UE allocates the high priority to theuplink transmission of the cell group with the low uplink requiredtransmission power and, otherwise if it the difference (or ratio) isless than the threshold, the UE allocates the high priority to theuplink transmission of a cell group (e.g., an MCG).

The method 3 is conceived by taking notice that if the transmit powerdifference is noticeable it is preferred to reduce the transmit power ofthe uplink with the required high transmit power and, otherwise if thetransmit power difference is not noticeable, it is preferred to reducethe transmit power of more important signal.

The UE determines the priorities among the uplink transmissions in eachcell group as follows.

Intra-Cell Group Priority Determination Method

If PUCCH and PUSCH transmissions are overlapped, the UE allocates a highpriority for the PUCCH transmission.

If the PUSCH transmissions are overlapped, the UE allocates a highpriority to the PUCCH transmitted with the Uplink Control Information(UCI). If there is no PUSCH transmitted with UCI, the UE allocates thesame priority for the PUSCH transmissions.

The UE decreases the transmit powers of the uplink transmission to whichthe same priority is allocated in the same degree. For example, theequal power scaling is applied to the transmit powers of the uplinktransmission allocated the same priority. In the case that differentpriorities are allocated to the uplink transmissions, the transmit powerof the uplink transmission with the low priority is reduced withpriority. For example, the differential power scaling is applied to thetransmit powers of the uplink transmissions allocated differentpriorities.

Table 4 shows a case of transmit power control according to the2-operation priority determination in the case of applying the cellgroup priority determination method 3. Table 4 is directed to the casewhere the uplink required transmit power difference between MCG and SCGis equal to or greater than a certain threshold.

TABLE 4 Maximum allowed transmit power of UE at a certain time point =80.8 mW MCG SCG PUCCH1 PUSCH1 PUSCH2 PUCCH2 PUSCH3 PUSCH4 Required Txpower SCG 100 mW 200 mW 0.01 mW 0.02 mW 0.05 mW Tx power after 50 mW  10mW  20 mW 0.01 mW 0.02 mW 0.05 mW adjustment No Tx power Equal powerscaling No Tx power reduction reduction

Referring to FIG. 4, the maximum allowed transmit power of the UE is80.8 mW, and the sum of the required transmit powers is 350.8 mW. The UEallocates priorities for determining the uplink transmission for whichthe transmit power is to be reduced.

The UE determines whether difference (ratio) between the total MCGrequired transmit power (350 mW) and the total SCG required transmitpower (0.08 mW) is equal to or greater than a certain threshold (e.g.,20 dB). Since the difference between the total MCG required transmitpower and the total SCG required transmit power is greater than thethreshold, the UE allocates the high priority to the SCG uplinktransmission of which total transmit power is low (determinationoperation 1).

The UE determines the priorities among the uplink transmissions in theMCG and the priorities among the uplink transmissions in the SCG. AmongPUCCH 1 transmission, PUSCH 1 transmission (PUSCH transmission in a MCGserving cell), PUSCH 2 transmission (PUSCH transmission in another MCGserving cell) through MCG, the UE allocates the high priority for thePUCCH transmission and the low priority for the PUSCH 1 and PUSCH 2transmissions. Among the PUCCH 2 transmission (PUCCH transmission in thepSCell), PUSCH 3 transmission (PUSCH transmission in an SCG servingcell), and PUSCH 4 transmission (PUSCH transmission in another SCGserving cell), the UE allocates the high priority for the PUCCH 2transmission and the low priority to the PUSCH 3 and PUSCH 4transmissions (second determination operation).

Since the cell group priority has priority over the cell priority, thefinal priorities are determined as follows:

-   -   The highest priority: PUCCH 2 transmission.    -   The second highest priority: PUCCH 3 and PUCCH 4 transmissions.    -   The third highest priority: PUCCH 1 transmission.    -   The lowest priority: PUSCH 1 and PUSCH 2 transmissions.

The UE reduces the transmit power of the uplink transmission with thelowest priority first. In the example of Table 4, the UE has to reducethe transmit power as much as 270 mW corresponding to the power amountwhich is obtained by subtracting the maximum allowed transmission power(80.08 mW) from the total required transmit power (350.08) by reducingthe transmit powers of the PUSCHs 1 and 2 to 1/10, it is possible toreduce the transmit power as much as 270 mW such that the UE reduces thetransmit power as much as 270 mW by applying the equal power scaling tothe PUSCHs 1 and 2 while maintaining the transmit powers for otheruplink transmissions.

If the total required transmit power is greater than the maximum allowedtransmit power of the UE after reducing the transmit power of the uplinktransmission with the lowest priority to OmW, the UE controls thetransmit power of the uplink transmission with the next lowest priority,i.e., the third highest priority.

The UE repeats the above process until the controlled total requiredtransmit power is not greater than the maximum allowed transmit power ofthe UE.

FIG. 7 is a flowchart illustrating an uplink transmit power controlprocedure of a UE according to an embodiment of the present disclosure.

Referring to FIG. 7, if the UE receives an uplink grant, if there isuplink grant configured to the UE, if the UE has to performretransmission, or if the UE has to transmit PUCCH, the UE operates asshown in FIG. 7. The configured uplink grant relates to the uplinktransmission resource occurring periodically and complies with the3^(rd) Generation Partnership Project (3GPP) standard TS36.321.

The UE determines a first operation real transmit power for uplinktransmission to be performed at a subframe at operation 705. If severaluplink transmissions are scheduled, the UE determines the firstoperation real transmission power per transmission. The first operationreal transmission power is the transmission power calculated per servingcell and is the smallest one between the required transmit power and themaximum allowed transmit power of the UE in the serving cell.

The required transmit power of PUSCH is calculated by Equation (1) basedon the pathloss, PUSCH transmission bandwidth (or number of PRBs), PUSCHtransmission format (Modulation and Coding Scheme (MCS), andTransmission Power Command (TPC). The calculation complies with the 3GPPstandard TS 36.213.

10 log(M _(PUSCH,c)(i))+P _(0_PUSCH,c)(j)+c(j)·PL _(c)+Δ_(TF,c)(i)+f_(c)(i)   Equation (1)

Assuming the maximum allowed transmit power of the UE at subframe I in aserving cell c is P_(CMAX,c)(i), the first operation real transmissionpower of PUSCH is calculated by Equation (2). The calculation complieswith the 3GPP standard TS 36.213.

$\begin{matrix}{{P_{{PUSCH},c}(i)} = {\min \left\{ \begin{matrix}{{P_{{CMAX},c}(i)},} \\{{10\; {\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{{0\_ \; {PUSCH}},c}(j)} + {{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{matrix} \right.}} & {{Equation}\mspace{14mu} (2)}\end{matrix}$

Assuming the maximum allowed transmit power of the UE at subframe I in aserving cell c is P_(CMAX,c)(i), the first operation real transmissionpower of PUCCH is calculated by Equation (3). The calculation complieswith the standard TX 26.213.

$\begin{matrix}{{P_{PUCCH}(i)} = {\min \left\{ \begin{matrix}{{P_{{CMAX},c}(i)},} \\{P_{0\; \_ \; {PUCCH}} + {PL}_{c} + {h\left( {n_{CQI},n_{HARQ},\; n_{SR}} \right)} + {\Delta_{F\; \_ \; {PUCCH}}(F)} + {\Delta_{T\; {xD}}\left( F^{\prime} \right)} + {g(i)}}\end{matrix} \right.}} & {{Equation}\mspace{14mu} (3)}\end{matrix}$

Briefly, the first operation real transmit power of PUCCH is determinedbased on the amount and format of the information transmitted on PUCCH.The first operation real transmission power is the real transmit powerper serving cell and may be adjusted finally in accordance with thetotal maximum allowed transit power of the UE.

The UE compares the sum of the first operation real transmit powers andthe maximum allowed transmit power P_(CMAX)(i) of the UE at operation710. The maximum allowed transmit power of the UE at a subframe i isdetermined based on the physical maximum output power and per-cellallowed value as specified in the standard TX 36.101.

If the sum of the first operation real transmit powers is not greaterthan the maximum allowed transmit power of the UE, there is no need ofadjusting the transmit power and thus the UE sets the respective realuplink transmit powers to the first operation real transmit powers atoperation 715 and ends the procedure.

If the sum of the first operation real transmit powers is greater thanthe maximum allowed transmit power of the UE, the procedure goesoperation 720 to adjust the transmit powers. At operation 720, the UEdetermines whether any SCG is configured (or DC is configured or aplurality of CGs are configured) and, if any SCG is configured (or DC isconfigured or a plurality of CGs are configured), the procedure goes tooperation 730 and, otherwise, operation 725.

At operation 730, the UE determines whether to perform uplinktransmission through multiple cell groups (or through both the MCG andSCG) and, if so, the procedure goes to operation 735 and, otherwise,operation 725.

If the procedure goes to operation 725, this indicates that the uplinktransmission is performed through one cell group and thus the UE doesnot need to determine the cell group priorities but the priorities amongthe uplink transmissions of the cell group. Otherwise if the proceduregoes to operation 735, this means that the uplink transmission isperformed through multiple cell groups and thus the UE has to determinethe cell group priorities and then the per-cell group uplinktransmissions priorities.

At operation 725, the UE determines the priorities among the uplinktransmissions using the cell group priority determination methodaccording to an embodiment of the present disclosure. The cell grouppriority determination method is performed as described above. Forexample, the UE may allocate to the PUCCH transmission a priority higherthan that of the PUSCH transmission.

At operation 735, the UE determines the priorities of the cell groupsusing the cell group priority determination method according to anembodiment of the present disclosure. The cell group prioritydetermination method is performed as described above. For example, ifthe difference (or ratio) between the sum of the first operation realtransmit powers of MCG uplink transmissions and the sum of the firstreal transmit powers of the SCG uplink transmissions is less than acertain threshold, the UE allocates the high priority to the MCG uplinktransmissions and, otherwise if the difference (or ratio) is equal to orgreater than the threshold, allocates the high priority to the cellgroup of which the sum of the first operation real transmission powersis low (or the cell having the low first operation real transmissionpower, if the uplink transmission is performed through one cell).

The UE determines the priorities of the uplink transmissions in the cellgroup using the intra-cell group priority determination method accordingto an embodiment of the present disclosure at operation 740. If only oneuplink transmission is scheduled in the cell group, operation 740 may beomitted.

The UE determines priorities among the uplink transmissions finally atoperation 743. For example, the UE allocates the highest priority to thePUCCH transmissions or the PUCCH transmission including UCI in the cellgroup with the high priority, the next highest priority to the PUSCHtransmissions in the cell group with the highest priority, the nexthighest priority to the PUCCH transmission or the PUSCH transmissionincluding UCI in the cell group with the low priority, and the lowestpriority to the PUSCH transmission in the cell group with the lowpriority.

At operation 745, the UE adjusts (controls) the transmit powers based onthe priorities determined as above. The UE reduces the transmit power ofthe uplink transmission with the lowest priority first to maintain thesum of the transmit powers below the maximum allowed transmit power. Ifthe sum of the transmit powers of the uplink transmission even afterreducing the transmit power of the uplink transmission with the lowestpriority to 0 mW, the UE adjust the transmit power of the uplinktransmission with the next lowest priority. The UE repeats this processuntil the sum of the transmit powers is not greater than the maximumallowed transmit power.

The UE sets the final transmit powers of the corresponding uplinktransmissions to the value obtained by reducing the first operation realtransmit powers of the respective uplink transmissions at operation 750and ends the procedure.

In an embodiment of the present disclosure, the UE may allocate priorityto the PUCCH transmission independently of the cell group and apply theequal power scaling or the differential power scaling to the PUSCHtransmissions. For example, if the sum of the first operation realtransmit powers is greater than the maximum allowed transmit power ofthe UE, the UE may allocate the highest priority to the PUCCH and thePUSCH including UCI (i.e., it is possible to reduce the transmit powerwhen the total required transmit power is greater than the maximumallowed transmit power even when the transmit power of the uplinktransmission with the low priority is reduced to 0 mW). The UE mayallocate the same priorities to the PUSCH transmissions (i.e., apply theequal power scaling) or, if the difference (or ratio) between the firstoperation real transmission powers is greater than a certain threshold,allocate the priority to the PUSCH transmission with low first real timetransmit power (i.e., reduce the transmit power of the PUSCH with thehigh first operation real transmission power with priority. Adescription is made thereof in the following situation.

-   -   First operation real transmit power of uplink transmission to        occur at certain time duration (e.g., one subframe),    -   First operation real transmit power of the PCell        PUCCH=P_(PCellPUCCH) mW,    -   First operation real transmit power of PUCCH of MCG SCell        1=P_(SCell1) mW,    -   First operation real transmit power of PUSCH of SCG        SCell2=P_(SCell2UCI) mW,    -   First operation real transmit power of PUSCH of SCG        SCell3=P_(SCell3) mW,    -   The PUSCH transmission of SCG SCell2 includes UCI,    -   P_(PCellPUCCH)+P_(SCell)+P_(SCell2UCI)+P_(SCell3)>PCMAX, and    -   P_(SCell)/P_(SCell3)>TH1 (e.g., centuple).

In the above case, since the highest priority is allocated to the PUCCHand PUSCH including UCI, the power headroom available for the MCG SCell1 and SCG SCell 3 with the low priority is[P_(CMAX)−(P_(PCellPUCCH)+P_(SCell2UCI))] mW.

Since the ratio between the PUSCH transmit powers of the MCG SCell 1 andthe SCG SCell 3, the UE allocates a higher priority to the uplinktransmission with the low transmit power. Accordingly, the powerheadroom available for the MCG SCell 1 with the lowest priority is[P_(CMAX)−(P_(PCellPUCCH)+P_(SCell2UCI)+P_(SCell3))] mW.

If the power headroom is equal to or greater than 0, the UE adjusts thetransmit power of the PCell1 to configure the real transmit power of theSCell 1 and the transmit powers of the rest uplink transmissions at setto the first real transmit powers as they are. If the power headroom isless than 0, the required transmit power exceeds the maximum allowedtransmit power of the terminal even though the real trans power of theSCell 1 is set to 0 and thus the UE sets the real transmit power of theSCell 1 to 0 and adjusts the transmit power of the uplink transmission,i.e., PUSCH of the SCell 3, with the priority higher than that of thePUSCH of the SCell 1. For example, if the calculation result is equal toor greater than 0, the UE adjusts the transmit power of the SCell 3 to[P_(CMAX)−(P_(PCellPUCCH)+P_(SCell2UCI))] mW.

The UE repeats the above process until the sum of the controlledtransmit powers becomes not greater than the maximum allowed transmitpower.

FIG. 8 is a flowchart illustrating an uplink transmit power controlprocedure of a UE according to an embodiment of the present disclosure.

Referring to FIG. 8, the UE selects one of the equal power scaling andthe differential power scaling depending on the difference between thetransmit powers.

Operations 805, 810, and 815 are identical with operations 705, 710, and715 in FIG. 7.

If the sum of the first operation real transmit powers is greater thanthe maximum allowed transmit power at operation 810, the procedure goesto operation 817. At operation 817, the UE determines whether the firstoperation transmit power difference between PUSCH transmissions, amongthe uplink transmissions, is greater than a certain threshold (TH1). Atthis time, the UE may consider the PUSCH transmissions including no UCIamong the PUSCH transmissions. In the above described embodiment of thepresent disclosure, the UE compares P_(SCell1) and P_(SCell3) with eachother and determined whether the ratio therebetween is greater than TH1.If the ratio or difference is greater than TH1, the UE applies thedifferential power scaling at operation 820 and, otherwise equal to orless than TH1, the equal power scaling at operation 825.

If there are more than two PUSCH transmissions, the UE takes ratios ofall available combinations into consideration and applies thedifferential power scaling to the combinations that fulfils the abovecondition at operation 820 and the equal power scaling to thecombinations that do not fulfil the above condition at operation 825.For example, if there are P_(SCell_x) (first operation real transmitpower of SCell_x), P_(SCell_y), and P_(SCell_z), the UE determineswhether there is any combination of which difference is greater than TH1among the all available combinations [P_(SCell_x), P_(SCell_y)],[P_(SCell_x), P_(SCell_z)], and [P_(SCell_y), P_(SCell_z)]. The UEapplies the equal power scaling to the combination, e.g., [P_(SCell_x),P_(SCell_y)], of which difference is greater than TH1 and thedifferential power scaling to the combination, e.g., [P_(SCell_x),P_(SCell_z)], of which difference is equal to or less than TH1.

According to another embodiment of the present disclosure, one of allavailable combinations shows the difference greater than TH1, theprocedure goes to operation 820 at which the UE applies the differentialpower scaling to all the PUSCH transmit powers and, when there is nocombination showing the difference greater than TH1, the procedure goesto operation 825 at which the UE applies the equal power scaling.

According to another embodiment of the present disclosure, the UEdetermines whether apply the equal power scaling or differential powerscaling based on the absolute values of the first operation realtransmit powers. For example, the procedure goes to operation 820 forthe uplink transmission of which transmit power is equal to or less thana certain threshold to apply the differential power scaling andoperation 825 for the uplink transmission of which transmit power isgreater than the threshold to apply the equal power scaling. Forexample, if the sum of the first operation real transmit powers at acertain time point is greater than P_(CMAX), the UE applies thedifferential power scaling to the uplink transmission of which firstoperation real transmit power is equal to or less than a certainthreshold and the equal power scaling to the uplink transmission ofwhich first operation real transmit power is greater than the threshold.For example, if the first operation real transmit powers of PUSCH 1,PUSCH 2, PUSCH 3, and PUSCH 4 are 100 mW, 400 mW, 0.5 mW, and 0.9 mWrespectively, and the certain threshold is 0 dBm (1 mW). The UE appliesthe differential power scaling to PUSCHs 3 and 4 of which firstoperation real transmit powers are less than 1 mW (i.e., allocates thehigh priority and dos not reduce the transmit powers before the transmitpower of the uplink transmission with low priority decreases to 0 mW)and the equal power scaling to the PUSCHs 1 and 2 (i.e., allocates thelow priority and reduces the transmit powers at the same rate).

If the differential power scaling is applied to an uplink transmission,this indicates that applying the high priority to the correspondinguplink transmission and to reduce the transmit power with the lowpriority first. If the equal power scaling is applied to an uplinktransmission, this indicates that the low priority is applied to thecorresponding uplink transmission to reduce the transmit powers of theuplink transmissions with the low priority at the same rate.

At operation 820, the UE applies the differential power scaling to thePUSCH transmit powers. For example, the UE reduces the transmit power ofthe PUSCH transmission with the highest transmit power and, if thetransmit power shortage state is not resolved even after reducing thehighest transmit power to OmW, reduces the next highest transmit power.This process is performed repeatedly until the transmit power shortageis resolved.

At operation 825, the UE applies the equal power scaling to the PUSCHtransmit powers. For example, the UE reduces the PUSCH transmit powersat the same rate until the transmit power shortage state is resolved.

The UE determines whether the transmit power shortage state is resolvedat operation 830 and, if resolved, the procedure goes to operation 835and, otherwise, operation 840. At operation 835, the UE sets the uplinktransmit power of the uplink transmission without power reduction to thefirst operation real transmit power and the uplink transmit power of theuplink transmission with power reduction to the value obtained bysubtracting the reduced transmit power from the first operation realtransmit power.

If the procedure goes to operation 840, this indicates that the transmitpower shortage state is not resolved even though the PUSCH transmitpower (except for PUSCH including UCI) is reduced to 0 mW and this theUE determined whether the difference between the first operation realtransmit power of the PUCCH and the first operation real transmit powerof the PUSCH including UCI is greater than a certain threshold TH2 toadjust the PUCCH transmit power. In the above-described embodiment ofthe present disclosure, the UE determines whether the difference betweenP_(SCell2UCI) and P_(PCellPUCCH) is greater than TH2. If the PUCCH istransmitted through both the MCG and SCG or if the PUSCH including UCIis transmitted through both the MCG and SCG, the UE determines whetherthe difference between their real transmit powers is greater than TH2.

If the first operation real transmit power difference between the twouplink transmissions is greater than TH 2, the UE applies thedifferential power scaling at operation 845 and, otherwise, the equalpower scaling at operation 847.

The UE reduces the transmit power of the PUCCH transmission or PUSCHtransmission including UCI which is allocated the high priority first atoperation 845. The UE reduces the transmit powers of the PUCCHtransmissions at the same rate at operation 847. In addition, the UE mayreduce the transmit powers of the PUCCH transmission and the PUSCHtransmission including UCI at the same rate.

In another approach, the UE determines the absolute values of the firstoperation real transmit powers of PUCCH and PUSCH including UCI insteadof considering the difference between the first operation realtransmission power of the PUCCH and the first operation real transmitpowers of the PUSCH including UCI. In this case, it is possible to applythe low priority to the uplink transmission of which transmit powerabsolute value is greater than another threshold (e.g., 2 mW) to reduceits transmit power first and to apply the high priority to the uplinktransmission of which transmit power absolute value is equal to or lessthan the threshold subsequently to reduce it transmit power. If thefirst operation real transmit powers of the two uplink transmissions aregreater than the threshold, the UE applies the equal power scaling tothe two uplink transmissions.

FIG. 13 is a flowchart illustrating an uplink transmit power controlprocedure of a UE according to an embodiment of the present disclosure.

Referring to FIG. 13, the UE determines the priorities among the uplinktransmissions based on their importance.

The uplink transmissions of the UE can be classified as shown in Table5. The details of the signals enumerated herein comply with the 3GPPstandard TS36.211, 36.212, 36.213, and 36.321.

TABLE 5 Preamble This is a UL signal for random access. Part of the ULtransmission resource is reserved for preamble transmission. The UE cantransmit preamble in a PCell, a pSCell, or an SCell having random accessinformation. Scheduling Request This is a UL signal for transmissionresource request. Part of the PUCCH resource can be allocated to UE asSR transmission resource. The UE can transmit SR in a PCell or a pSCell.HARQ feedback This is the HARQ feedback signal corresponding PDSCH andtransmitted on the PUSCH resource of a PCell or a pSCell. CSI (ChannelState This is a signal indicating DL signal quality. Part of theInformation) PUCCH resource may be allocated to the UE as CSItransmission resource. The UE can transmit CSI in a PCell or a pSCell.SRS (Sounding This is a reference signal transmitted by UE in uplink foruse Reference Signal) in uplink channel estimation at the eNB. SRS canbe configured to all serving cells and transmitted at the last symbol ofPUSCH transmission resource. PUSCH This is the UL channel carrying userdata (MAC PDU).

If DC is configured, various uplink signals may collide one another. TheUE determines the collided signals and determines the priorities amongthe uplink signals.

The basic principle is to allocate, to the uplink signal which is likelyto be concerned with RRC control message transmission, a priority higherthan those of other uplink signals because the very important data,e.g., an RRC control message, may be transmitted through the MCG.Examples of the uplink signal which is likely to be concerned with theRRC control message transmission include the preamble transmitted in thePCell, the scheduling request transmitted in the PCell, and PUSCHtransmitted in an MCG service cell.

FIG. 6 shows the priorities among the uplink signals according to anembodiment of the present disclosure.

TABLE 6 Priorities between MCG UL SCG and SCG UL Preamble SR A/N CSI SRSPUSCH MCG Preamble Allocate priority to MCG Preamble transmission SRAllocate priority to NCG SR transmission A/N MCG MCG MCG SCG MCG MCG A/NA/N A/N CSI A/N A/N CSI SCG SCG SCG SCG MCG MCG Preamble SR A/N CSI CSICSI SRS SCG SCG SCG SCG A-SRS SCG Preamble SR A/N CSI PUSCH PUSCHAllocate priority to MCG PUSCH transmission

The MCG ACK/NACK (A/N) (HARQ feedback) is likely to be a feedbackcorresponding to an RRC message. Accordingly, it is preferred toallocate to the MCG A/N a priority higher than those of other SCG uplinksignals. However, since the SCG CSI is important informationguaranteeing the efficiency of large volume PDSCH transmission in theSCG, the priority is given to the SCG CSI when the MCG A/N and SCG CSIcollide.

Since the MCG is likely to be used to transmit small data, such as RRCmessages, the MCG CSI is not so important. Accordingly, when the MCG CSIand SCG CSI collide or the MCG CSI and the SCG preamble collide, a lowpriority is allocated to the MCG CSI.

The SRS may be classified into one of Periodic SRS and aperiodic SRS(A-SRS) and, when the MCG SRS and the SCG SRS collide and one of them isA-SRS, the priority is given to the A-SRS. This is because the A-SRStransmission is commanded by the eNB and thus is more important than theperiodic SRS which is transmitted by the UE autonomously. When both theSRSs are A-SRSs or when none of the SRSs are A-SRSs, the priority isgiven to the MCG SRS. This is because the MCG uplink channel state islikely to be more important than the SCG uplink channel state.

If there is no doubt that the MCG preamble, SR, and PUSCH are notrelated to the RRC control message, e.g., if the MCG SR or the bufferstatus report triggered random access is not triggered by occurrence ofan RRC control message but the RRC control message is contained in theMAC PDU related to the PUSCH transmission, the priorities are determinesby applying Table 7.

The basic principle that the priority is allocated in the order ofpreamble transmission, HARQ A/N transmission, SR transmission, CSItransmission, PUSCH transmission, and SRS transmission, when the uplinktransmissions collide one another and, if the same types oftransmissions collide, determine priorities thereof based on thetransmission type. The priority is given to MCG A/N in collision betweenMCG A/N and SCG A/N, MCG SR in collision between MCG SR and SCG SR, SCGCSI in collision between MCG CSI and SCG CSI, and MCG PUCCH in collisionMCG PUSCH and SCG PUSCH, and, in collision between SRSs, according tothe rule in Table 7.

TABLE 7 Priorities between MCG UL SCG and SCG UL Preamble A/N SR CSI SRSPUSCH MCG Preamble MCG Preamble Preamble Preamble Preamble Preamble A/NPreamble A/N A/N A/N A/N A/N SR Preamble A/N MCG SR SR SR CSI PreambleA/N SR SCG CSI CSI SRS Preamble A/N SR CSI A-SRS PUSCH PUSCH PreambleA/N SR CSI PUSCH MCG

FIG. 13 is a flowchart illustrating an uplink transmit power controlprocedure of a UE according to an embodiment of the present disclosure.FIG. 13 is directed to the UE operation for uplink transmission at asubframe.

Since operations 705, 710, 715, 720, 730, 745, and 750 are identicalwith those of FIG. 7, descriptions thereof are omitted herein.

At operation 1325, the UIE determines the priorities of the uplinktransmissions according to the priority determination method 3(embodiment of FIG. 13). The priority determination method 3 allocatespriority in the order of preamble transmission, HARQ A/N transmission,SR transmission, CSI transmission, PUSCH transmission, and SRStransmission.

At operation 1335, if condition 1 is fulfilled, the UE determines thepriorities according to Table 6 and, otherwise, Table 7. If one of theMCG preamble transmission, SR transmission, and PUSCH transmissionrelates to the RRC control message transmission, condition 1 isfulfilled and, otherwise, condition 1 is fulfilled. After determiningthe priorities according to Table 6 or 7, the procedure goes tooperation 745.

Operations 740 and 705 are identical with those of FIG. 7.

FIG. 9 is a diagram illustrating a situation where two uplink subframesare not aligned according to an embodiment of the present disclosure.The uplink subframe boundaries of the different cell groups maymismatch.

Referring to FIG. 9, the boundary of the subframe 905 of the MCG servicecells and the boundary of the subframe 910 of the SCG serving cells aredislocated as much as x as denoted by reference number 915, one MCGsubframe is overlapped with tow SCG subframes on the time axis. Forexample, the MCG subframe [n+1] 920 is overlapped with the SCG subframe[m+1] 925 and the SCG subframe [m+2] 945.

When determining the priorities of the uplink transmit powers at asubframe, the UE determines the uplink transmit power based on thesubframe selected among a plurality subframes overlapped with thesubframe according to a certain rule.

For example, if the MCG subframe [n+1] 920 carries PUSCH, the SCGsubframe [m+1] 925 carries PUCCH, and SCG subframe [m+2] 945 carriesnothing, the UE determines the transmit power of the MCG subframe [n+1]920 based on the transmit power of the subframe which is more overlappedwith the subframe [n+1] 920 in the time domain. Since the duration 930overlapped between the subframe [n+1] 920 and the subframe [m+1] 925 islonger than the duration 940 overlapped between the subframe [n+1] 920and the subframe [n+2] 945, the UE determines the transmit power of thesubframe [n+1] 920 based on the transmit power and transmission type(uplink data type, such as PUCCH, PUSCH, PUSCH including UCI, and thelike) of the subframe [m+1] 925.

Similarly, since the duration 930 overlapped between the subframe [m+1]925 and the subframe [n+1] 920 is longer than the duration 935overlapped between the [m+1] 925 and the subframe [n] 905, the UEdetermines the transmit power of the subframe [m+1] 925 based on thetransmit power and transmission type of the subframe [n+1] 920.

In the case of considering the subframe which is more overlapped in thetime domain, it may occur that the sum of the transmit powers is greaterthan the maximum allowed transmit power in the duration less overlappedsubframe (e.g., duration 940). If the transmit power shortage occurs inthe less overlapped duration, the UE may apply the equal power scalingto adjust the transmit power in the corresponding duration.

FIG. 10 is a signal flow diagram illustrating a signal processingprocedure for transmitting signals using multiple carriers at a UE in amobile communication system according to an embodiment of the presentdisclosure.

Referring to FIG. 10, if a certain condition is fulfilled in the LTEnetwork, a UE 1005 reports its capability to an MeNB 1010 at operation1025. The condition is fulfilled representatively when the eNB requestthe UE 1005 for UE capability.

The UE capability report message includes the information as follows.

-   -   List of frequency bands supported by UE 1005,    -   List of frequency band combinations supported by UE 1005, and    -   MIMO capability per frequency band combination.

In an embodiment of the present disclosure, the UE 1005 reports theinformation indicating whether DC is supported per frequency bandcombination supported by the UE 1005 along with the above information.The DC supportability is reported for the frequency band combinationfulfilling a certain condition. For example, if the DC supportabilityfor the frequency band combination in the same band (or combinationhaving one band entry, hereinafter referred to as intra-bandcombination) is not reported explicitly, this indicates that the DC isnot supported for the corresponding frequency band combination. The DCmay be supported for the frequency band combination across differentbands (or combination having two or more band entries, hereinafterreferred to as inter-band combination). The UE 1005 may reduce the sizeof the message by marking whether it support DC per band combination forthe inter-band combination.

If a certain event, e.g., if channel quality of a pico cell fulfils acertain condition, in the middle of data communication with the MeNB1010 in the macro cell are, the UE 1005 generates and transmits ameasurement report to the MeNB 1010 at operation 1030.

At this time, the measurement report message includes the information asfollows.

-   -   Identifier of the cell of which channel quality fulfils a        certain condition (e.g., physical layer cell identifier or        Physical Cell ID (PCI), and    -   Channel quality or reference signal strength of the        corresponding cell.

If the measurement report message is received from the UE 1005, the MeNB1010 becomes aware that the UE 1005 is in the pico cell area. The MeNB1010 determines to configure a pico cell (serving cell) to the UE 1005at operation 1035. The data transmission/reception through the pico cellis more efficient to the data transmission/reception through the macrocell in various respects. Accordingly, if the UE 1005 is located withinthe pico cell area, it is preferred for the eNB to configure the picocell in which the UE 1005 is located as a new serving cell.

The MeNB 1010 determines an SeNB 1015 controlling the pico cell byreferencing the identifier of the pico cell and transmits to the SeNB1015 a control message requesting to add a serving cell at operation1040.

The control message transmitted for serving cell add request includesthe information in Table 8.

TABLE 8 Name Description SCell ID This is the information related to theidentifiers of the SCells to be Information configured by SeNB. Thisincludes one or more SCellIndex-r10. This is determined by the MeNB andsent to the SeNB to prevent the identifier in use by the MeNB from beingreused. TAG ID This is the information related to the identifier of TAGto be Information configured by SeNB. This is determined by the MeNB andsent to the SeNB to prevent the identifier in use by the MeNB from beingreused. UL scheduling This includes the priority information of thelogical channels information configured at the UE and logical channelgroup information. The SeNB interprets the buffer status reportinformation of the UE and performs uplink scheduling based on thisinformation. Data rate This is the DL/UL predicted data rateinformation. The SeNB information determines whether to accept or rejectthe SCell add request based on this information. Information on The DRB(Data Radio Bearer) is the radio bearer established for DRB to beprocessing user plane data. If the UE enters a pico cell area, all userserved by plane data or most user plane data are processed preferablythrough SeNB the pico cell. The MeNB transmits to the SeNB theinformation on the DRBs to be processed through the pico cell, e.g.,PDCP configuration information (PDCP header structure, header compressprotocol information, and the like), RLC information (RLC operationmode, timers, and the like), logical channel information (logicalchannel identifier, priority, and the like). The SeNB determines thefinal DRB configuration information based on the above information.Measurement The UE report the channel quality information transmitted inthe quality measurement report message to the SeNB. The SeNB determinesinformation of whether to accept or reject the serving cell add requestbased on this serving cell information and the data rate information.requested to be configured additionally

The SeNB 1015 determines whether to accept or reject the serving celladd request based on the serving channel information and UE data rateinformation.

If it is determined to accept, the SeNB 1015 establishes one or moreDRBs at operation 1045. Afterward, the SeNB 1015 processes the datatransmitted by and to be transmitted to the UE 1005 through the DRB.

If the SeNB 1015 establishes a DRB, this indicates to establish PDCP andRLC entities for processing data requiring a certain QoS. The DRBconfiguration may be identical with or different from the originalconfiguration notified by the source eNB (HeNB) 1010.

The SeNB 1015 transmits to the MeNB 1010 a control message for acceptingthe SCell add request at operation 1050. This control message includesthe information in Table 9.

TABLE 9 Name Description SCellToAddMod This is the information on theSCells configured in the SeNB and includes the information as follows.SCellIndex-r10, cellIdentification-r10,radioResourceConfigCommonSCell-r10,radioResourceConfigDedicatedSCell-r10, and TAG information. PUCCHPhysical Uplink Control Channel (PUSCH) is configured in at leastinformation for one of the SCells belonging to SCG. The UL controlinformation, pSCell such as HARQ feedback, Channel Status Information(CSI), Sounding Reference Signal (SRS), and Scheduling Request (SR) aretransmitted on PUCCH. The SCell in which PUCCH is transmitted isreferred to as PUCCH SCell hereinafter. This information includessub-information, such as PUCCH SCell identifier and PUCCH configurationinformation. Information for This is the information on the logicalchannel for use in data data forwarding exchange between MeNB and SeNBand includes GPRS Tunnel Protocol (GTP) tunnel identifiers for therespective DL and UL data exchanges. UE identifier This is C-RNTI to beused by the UE in the SCG SCell. DRB If identical with the DRBconfiguration used in the MeNB, this may configuration be omitted.information List of DRBs to DRB relocation is described below. If thelocations of all the DRBs be relocated are reconfigured, thisinformation may be omitted. Scheduling This is the information relatedto scheduling, such as Buffer Status information Report (BSR) and PowerHeadroom Report (PHR), e.g., triggering processing- condition andperiodic report cycle information. If identical with the relatedinformation of MeNB, this information may be omitted. information

The MeNB 1010 receives the SCell add response message from the SeNB 1015and stops downlink operation of the DRB to be relocated at operation1055. For example, the downlink data transmission stops on the DRB.However, the uplink data processing on the DRB is continued.

The MeNB 1010 generates an RRC control message for serving cell addrequest and transmits this message to the UE 1005 at operation 1060.This control message includes the information in Table 10.

TABLE 10 Name Description SCellAddMod The information transmitted by theSeNB is contained without modification. For example, SCellAddMod isidentical with that of Table 3. SCellAddMod is contained per SCell andsub-information of an SCellAddModList. PUCCH The information transmittedby the SeNB is contained without information for modification. Forexample, PUCCH information for pSCell is pSCell identical with that ofTable 3. SCGSCell List This is the information on the SCells belongingto the SCG among the configured SCells. This may include SCellidentifiers and identifiers of the TAGs belonging to the SCG. UEidentifier This is C-RNTI to be used by the UE in the SCG SCell. DRBInformation transmitted by the SeNB at operation 1050 configurationinformation List of DRBs Information transmitted by the SeNB atoperation 1050 to be relocated Scheduling Information transmitted by theSeNB at operation 1050 information processing- related informationTransmit Thresholds for transmit power control, such as TH1 and TH2.This is power the information notifying the uplink transmission to whichthe adjustment priority is given among the MCG and SCG uplinktransmissions. information

The above information is coded in the ASN. 1 coding scheme and thentransmitted to the UE 1005.

Upon receipt of the control message, the UE 1005 acquires downlinksynchronization with the newly configured SCell at operation 1065. Next,if a random access procedure for SCell is prepared, the UE 1005transmits to the MeNB 1010 a serving cell add response control messageat operation 1075.

More specifically, if the serving cell add response message isgenerated, the UE 1005 transmits D-SR in the PCell or initiates randomaccess procedure in the PCell to request for resource allocation totransmit the serving cell add response control message. If the uplinkresource is allocated by of cell of the MCG, the UE transmits to theMeNB 1010 the serving cell add response control message using theallocation resource.

If an HARQ ACK or an RLC ACK is received in correspondence to theserving cell add response control message, the UE starts the randomaccess procedure in a serving cell of the SCG at operation 1080. The SCGserving cell to perform the random access procedure is determinedaccording to the following method.

Method of Determining SCG Cell for Random Access Procedure

-   -   If there is one serving cell to which the random access        information is configured among the SCG serving cells, the UE        performs the random access in the corresponding serving cell.    -   If there is more than one serving cell to which the random        access information is configured among the SCG serving cells and        the random access information-configured cells includes the        pSCell, the UE performs the random access in the pSCell.

In the random access procedure, the UE 1005 transmits a preamble at asubframe on a frequency resource of the serving cell, receives aresponse message in response to the preamble, and performs uplinktransmission based on the control information included in the responsemessage.

If the random access procedure is completed as described above, the SeNB1015 determines that the UE is capable of data communication in the SCGSCell and schedules the UE 1050.

If it is necessary to perform multiple uplink transmissionssimultaneously, the UE determines whether the uplink transmissions areintra-cell group transmissions and, if intra-cell group transmissions,determines the priorities of the uplink transmissions according to acertain rule and, otherwise if inter-cell group transmissions,determines priorities of the uplink transmissions according to anotherrule at operation 1085. Here, the rules are the above-described rulesaccording to the various embodiments of the present disclosure.

After transmitting the serving cell add control message to the UE 1005,the MeNB 1010 performs a DRB relocation procedure with the SeNB 1015 andan S-GW 1020 at operation 1070. In the DRB relocation procedure, theMeNB 1010 transmits to the SeNB 1015 the DRB data to be processed by theSeNB 1015, releases the EPS bearers corresponding to the relocated DRBsamong the EPS bearers established between the S-GW 1020 and the MeNB1010, and reestablishes the EPS bearers between the S-GW 1020 and theSeNB 1015.

The UE 1005 may initiate the random access procedure in the SeNB 1015before transmitting the serving cell add response message so as to startdata transmission/reception as soon as possible. For example, if therandom access is prepared in the SCell after the receipt of the servingcell add control message, the UE 1005 starts the random access procedureimmediately. The serving cell add response message may be transmittedafter the random access procedure is completed or in the middle of therandom access procedure. At this time, the UE 1005 transmits the servingcell add response message when the uplink transmission resource of theMCG serving cell is available for transmitting the serving cell addresponse message to the MeNB 1010.

Another embodiment of the present disclosure proposes a UE procedure ofdetermining the RNTI to be received through monitoring based on the cellgroups.

The RNTI is the information indicating the UE to which the DownlinkControl Information (DCI) transmitted on PDCCH is addressed andsub-classified as follows in Table 11. The details of the RNTIs complywith the 3GPP standard TS36.211, 36.212, 36.213, 36.321, and 36.331.

TABLE 11 RNTI Usage P-RNTI Paging and System Information changenotification SI-RNTI Broadcast of System Information M-RNTI MCCHInformation change notification RA-RNTI Random Access Response TemporaryC-RNTI Contention Resolution (when no valid C-RNTI is available) C-RNTIDynamically scheduled unicast transmission Semi-PersistentSemi-Persistently scheduled unicast transmission Scheduling C-RNTI(activation, reactivation and retransmission) TPC-PUCCH-RNTI Physicallayer Uplink power control TPC-PUSCH-RNTI Physical layer Uplink powercontrol

In the case that the Dual Connectivity (inter-eNB carrier aggregation)is configured, the SeNB and MeNB may transmit to the UE the DCI andPDSCH using different RNTIs. The RNTI-related operations are summarizedin Table 12.

TABLE 12 RNTI allocation range RNTI-monitoring UE RNTI acquisition andallocator operation method C-RNTI Allocated per cell UE monitors MCGC-RNTI_(MCG) is allocated group, up to 2 C-RNTIs serving cell PDCCH forthrough RRC per UE. MCG C-RNTI C-RNTI_(MCG) and SCG Connection(C-RNTI_(MCG)) and SCG serving cell PDCCH for Reconfiguration C-RNTI(C-RNTI_(SCG)) C-RNTI_(SCG). message in the RRC are determined byconnection MeNB and SeNB establishment respectively and may procedure orhandover differ from each other. procedure, and C-RNTI_(SCG) isallocated through a control message configured by pSCell. SPS C-RNTIAllocated for PCell and If SPS is configured in SPS C-RNTI is pSCell, upto 2 SPS MCG, the UE monitors allocated through the C-RNTIs per UE. TheSPS the PCell PDCCH for RRC connection C-RNTI for PCell (SPS SPSC-RNTI_(PCELL). If reconfiguration C-RNTI_(PCELL)) and SPS SPS isconfigured in message containing C-RNTI for pSCell SCG, the UE monitorsSPS configuration (SPS C-RNTI_(PSCELL)) are the pSCell PDCCH forinformation (SPS- determined by MeNB SPS C-RNTI_(PSCELL). If config).and SeNB respectively SPS is used in a PCell, and may differ from and ifSPS is each other. In the case configured, the UE that SPS is used inthe monitors the PCell PCell, the UE may be PDCCH for SPS allocated oneSPS C-RNTI. C-RNTI. TPC- Allocated for PCell and If the TPC-PUCCH-TPC-PUCCH- PUCCH- pSCell, up to 2 TPC- RNTI_(PCELL) is allocated,RNTI_(PCELL) is allocated RNTI PUCCH-RNTIs per UE. the UE monitors thethrough RRC The TCP-PUCCH- PCell PDCCH for Connection Setup RNTI forPCell (TPC- receiving TPC of a message or RRC PUCCH-RNTI_(PCELL)) andPCell PUCCH. If TPC- Connection TCP-PUCCH-RNTI for PUCCH-RNTI_(PSCELL)is Reconfiguration pSCell (TPC-PUCCH- allocated, the UE message, andTPC- RNTI_(PSCELL)) are monitors the pSCell PUCCH-RNTI_(PSCELL) isdetermined by the PDCCH for receiving allocated through RRC MeNB andSeNB TPC of a pSCell Connection respectively and may PUCCH.Reconfiguration differ from each other. message including pSCellconfiguration information. TPC- Allocated for PCell and If TPC-PUSCH-TPC-PUSCH- PUSCH- pSCell, up to 2 TPC- RNTI_(PCELL) is allocated,RNTI_(PCELL) is allocated RNTI PUSCH-RNTIs. The the UE monitors PCellthrough RRC TPC-PUSCH-RNTI for PDCCH for receiving Connection SetupPCell (TPC-PUSCH- TCP of a PCell message or RRC RNTI_(PCELL)) and theTPC- PUSCH. If TPC- Connection PUSCH-RNTI for PUCCH-RNTI_(PSCELL) isReconfiguration pSCell (TPC-PUSCH- received, the UE message, and TPC-RNTI_(PSCELL)) are monitors pSCell PUSCH-RNTI_(PSCELL) 

determined by the PDSCH for receiving pSCell is allocated MeNB and SeNBTPC of a pSCell through the RRC respectively and may PUCCH. Connectiondiffer from each other. Reconfiguration message including pSCellconfiguration information. P-RNTI One common RNTI is UE monitors PCellfor A certain RNTI is used. used across two cell P-RNTI. groups. SI-RNTIOne common RNTI is UE monitors PCell for A certain RNTI is used. usedacross two cell SI-RNTI. groups. RA-RNTI A plurality of RNTIs are UEtransmits a random A certain RNTI is used. reserved per serving accesspreamble in a cell. serving cell and monitors the serving cell forRA-RNTI. If the preamble has been transmitted in an MCG serving cell,the serving cell is the PCell and, otherwise if the preamble has beentransmitted in an SCG serving cell, the serving cell is pSCell. M-RNTIOne common RNTI is The UE monitors the A certain RNTI is used. usedacross two cell serving cell through groups. which MBMS service isreceived or to be received for M-RNTI

According to various embodiments of the present disclosure, RNTIs areclassified into various types as follows, and the UE performs distinctmonitoring operations according to the type of RNTI.

First type RNTI: A UE may be allocated the first type RNTI per cellgroup and up 2 first type RNTIs. The UE monitors all the serving cellsin the activated state for the first type RNTI. C-RNTI is included inthe first type RNTI.

Second type RNTI: A UE may be allocated the second type RNTI per cellgroup, and up to 2 second type RNTIs. The UE monitors a serving cell forthe second type RNTI. TPC-PUCCH-RNTI and TPC-PUSCH-RNTI are included inthe second type RNTI. The serving cell is PCell or pSCell.

The third type RNTI: A UE is allocated up to 1 third type RNTI for aspecific cell group. The UE monitors a serving cell of the correspondingcell group for the third type RNTI. SPS-RNTI is included in the thirdtype RNTI. The specific cell group is the MCG, and the serving cell isPCell.

Fourth type RNTI: A UE is allocated up to 1 fourth RNTI for a specificcell group. The UE monitors a serving cell of the corresponding cellgroup for the fourth type RNTI. The SI-RNTI and P-RNTI are included inthe fourth type RNTI. The specific cell group is MCG, and the servingcell is PCell. The third type RNTI and the fourth type RNTI aredifferent in that the third type RNTI has a UE-specific unique valueallocated through an RRC control message but the third type RNTI has avalue common to all UEs.

Fifth type RNTI: The fifth type RNTI is allocated per serving cellindependently of cell group, and a UE monitors the corresponding servingcell for the fifth type RNTI when a certain event (e.g., a random accesspreamble transmission) occurs. If the serving cell in which the eventoccurs is an MCG serving cell monitors the PCell and, otherwise if theserving cell in which the event occurs is a SCG serving cell, the pSCellfor the fifth RNTI. RA-RNTI is included the fifth type RNTI.

FIG. 14 is a flowchart illustrating a procedure of determining, at a UE,a serving cell to be monitored for receiving RNTI according to anembodiment of the present disclosure.

Referring to FIG. 14, the UE determines the allocated RNTI at operation1405. The UE is allocated at least one first type RNTI and one fourthtype RNTI and allocated the second type RNTI and the third type RNTIoptionally.

The UE determines the type of RNTI for which it monitors PDCCH in asubframe to determine the serving cell to monitor its PDCCH at operation1410. If the target RNTI is the first type RNTI, the procedure goes tooperation 1415, if the target RNTI is the second type RNTI, theprocedure goes to operation 1420, if the target RNTI is the third orfourth type RNTI, the procedure goes to operation 1425, and if thetarget RNTI is the fifth type RNTI, the procedure goes to operation1430.

At operation 1415, the UE monitors PDCCHs of the serving cells in theactivated state. More particularly, the UE monitors the MCG servingcells PDCCHs for the first type RNTI related to the MCG and the SCGserving cells PDCCHs for the first type RNTI related to the SCG.

At operation 1420, the UE monitors the PCell PDCCH for the second typeRNTI related to MCG and pSCell PDCCH for the second type RNTI related toSCG.

At operation 1425, the UE monitors the PCell PDCCH for the third orfourth type RNTI.

At operation 1430, the UE monitors the PCell or pSCell PDCCH for thefifth type RNTI of the cell in which the event has occurred. If the cellin which the event has occurred is an MCG serving cell, the UE monitorsthe PCell PDCCH and, otherwise if the cell in which the event hasoccurred is an SCG serving cell, the pSCell PDCCH.

FIG. 15 is a diagram illustrating an operation mechanism of a UE withtwo MAC entities 1505 according to an embodiment of the presentdisclosure.

Referring to FIG. 15, the UE is provided with two MAC entities 1505. Inthis case, one MAC entity is responsible for MCG serving cell-relatedoperation and the other for SCG serving cell-related operation.

In the following description, MAC entities 1505 are classified intovarious types as follows for explanation convenience.

-   -   Normal MAC entity: MAC entity established when CA is not        configured or, although CA is configured, when all the        CA-available serving cells are controlled by one eNB (or when no        SCG is configured).    -   Primary MAC (P-MAC) entity 1510: MAC entity connected to the        serving cells controlled by the MeNB when at least one MAC        entity is established in the UE (i.e., when at least one serving        cell is configured to the UE and the at least one serving cell        is controlled by one eNB).    -   Secondary MAC (S-MAC) entity 1515: MAC entity connected to the        serving cells controlled by an SeNB when at least one MAC entity        is established in the UE (i.e., when at least one serving cell        is configured to the UE and the at least one serving cell is        controlled by at least one eNB).

The normal MAC entity connects all the logical channels configured inthe UE to the serving cells in the activated state among all servingcells configured to the UE.

The S-MAC entity connects certain logical channels among the logicalchannels configured in the UE to serving cells among all serving cellsconfigured to the UE. The serving cells are the serving cells under thecontrol of the SeNB and are indicated by an RRC control messageexplicitly. The logical channels are the logical channels indicated bythe RRC control message explicitly.

The P-MAC entity 1510 connects other logical channels among the logicalchannels configured in the UE to other serving cells of all servingcells configured to the UE. The other serving cells are the servingcells under the control of the MeNB and not included the serving cellsindicated explicitly by the RRC control message. A serving cell (e.g.,PCell) is connected to the P-MAC entity 1510. The other logical channelsare the logical channels except for the logical channels indicatedexplicitly by the RRC control message. A logical channel, e.g., DCCH, isconnected to the P-MAC entity 1510.

If certain logical channels are connected to certain serving cells (ortransport channels 1530 mapped to the serving cells), the data receivedthrough the serving cells are transferred to the logical channels andthe data occurred on the logical channels are transmitted through theserving cells.

A serving cell may consist of downlink which is referred to as DownlinkShared Channel (DL-SCH) and uplink which is referred to as Uplink SharedChannel (UL-SCH). Accordingly, the uplink 1520 of the serving cell #0may be referred to as UL-SCH of the serving cell #0, and the downlink1520 of the serving cell #5 as DL-SCH of the serving cell #5.

According to various embodiments of the present disclosure, the MACentity is responsible for connecting the logical channels and thetransport channels 1530.

The MAC entity is also responsible for random access function, ULtransmission timing maintenance function, Semi-Persistent Scheduling(SPS) function, Scheduling Request procedure (see TS36.321), BufferStatus Reporting procedure (see TS 36.321), Power Headroom Reportingprocedure (see TS36.321), and HARQ buffer management function.

In an embodiment of the present disclosure, when an event related to theMAC reset occurs, the UE resets the P-MAC 1510 and S-MAC 1515 entitiesselectively according to the type of the event.

FIG. 16 is a flowchart illustrating a MAC procedure of a UE according toan embodiment of the present disclosure.

Referring to FIG. 16, a certain MAC event occurs in the UE at operation1605. The MAC event is an event triggering MAC entity initialization,add, and release, e.g., handover and SCG add.

The UE determines whether the MAC event is a handover, or Radio LinkFailure (RLF), or SCG-related event at operation 1610. If the MAC eventis the handover event (i.e., if a handover command is received from theeNB), the procedure goes to operation 1615, if the MAC event is the RLFevent, operation 1620, and if the MAC event is the SCG-related event,operation 1630.

At operation 1615, the UE resets or releases the P-MAC or S-MAC. If thehandover command control message indicates SCG change, the UE resets theS-MAC and, otherwise if the handover command control message indicatesSCG release, releases the S-MAC.

At operation 1620, the UE determines whether the RLF has occurred in MCGor SCG.

If the RLF occurs in the MCG, this indicates that a state in which thechannel quality of a certain cell (e.g., a PCell) among the servingcells belonging to the MCG is below a certain threshold lasts over acertain duration.

If the RLF occurs in the SCG, this indicates that a state in which thechannel quality of a certain cell (e.g., a pSCell) among the servingcells belonging to the SCG is below a certain threshold lasts over acertain duration.

Here, the channel quality may be the channel quality of PDCCH.

If the RLF occurs in the MCG, this indicates that the UE cannot maintainthe current RRC connection any longer in the MCG and thus the UEperforms the RRC Connection Reestablishment procedure. At this time, theUE resets the P-MAC entity and releases the S-MAC entity.

If the RLF occurs in the SCG, this indicates that the UE cannot maintainthe current RRC connection any longer in the SCG. In this case, however,it is possible to maintain the normal communication through MCG.Accordingly, the UE maintains the current operation of the P-MAC entityand resets the S-MAC entity.

The reason for releasing the S-MAC while resetting the S-MAC atoperation 1625 is because it is likely to resume the multi-connectionoperation soon and it is necessary to stop uplink transmission throughMAC reset without release of the S-MAC entity for maintaining uplinktransmission through SCG in the case that the procedure goes tooperation 1627 while there is no need the S-MAC entity due to themulti-connection operation impossibility before finding a new PCell inthe case that the procedure goes to operation 1625.

At operation 1630, the UE determines whether the SCG-related event is anSCG change event, an SCG release event, or an SCG add event.

If the event is the SCG change event, i.e., if the control messagereceived from the eNB instructs to release the current SCG or add a newSCG, the UE maintains or resets the P-MAC entity and resets the S-MACentity at operation 1630. If the control message instructs handover too,the UE resets the P-MAC entity and, otherwise, maintains the P-MACentity. If the SCG is changed, this indicates that it is necessary tostop the MAC operation in the current SCG and starts the MAC operationnewly in a new SCG and thus the UE resets the S-MAC at operation 1635.

If the event is the SCG release event, i.e., if the control messagereceived from the eNB instructs to release the current SCG without anynew SCG add command, the UE maintains or resets the P-MAC entity andrelease the S-MAC entity at operation 1640. If the control messageinstructs handover too, the UE resets the P-MAC entity and, otherwise,maintains the P-MAC entity. If the SCG is released, this indicates thatit is necessary to stop the S-MAC entity and flush the HARQ buffer andthen deactivates the software and hardware related to the S-MAC entity.

If the event is the SCG add event, i.e., if the control message receivedfrom the eNB instructs to add a new SCG, the UE maintains or resets theP-MAC entity and adds a new S-MAC entity at operation 1645. If thecontrol message instructs handover too, the UE resets the P-MAC entityand, otherwise, maintains the P-MAC entity. Addition of the S-MAC entitymeans indicates it is necessary to activate the software and hardwarerelated to the S-MAC entity.

According to various embodiments of the present disclosure, it is alsopossible establishing a new S-MAC entity after releasing the S-MACentity instead of resetting the S-MAC entity.

The S-MAC and P-MAC entities reset operations are summarized in Table13.

TABLE 13 P-MAC entity reset S-MAC entity reset Stop/end TAGtimeAlignmentTimers Stop/end TAG timeAlignmentTimers configured to MCGconfigured to SCG Set NDIs (variable related HARQ initial Set NDIs ofHARQ processes of SCG transmission/retransmission) of HARQ serving cells(variable related HARQ processes of MCG serving cells to all 0. initialtransmission/retransmission) to all End ongoing random access procedures0. in a PCell and MCG serving cells End ongoing random access proceduresDiscard ra-PreambleIndex and ra- in a pSCell and SCG serving cellsPRACH-maskIndex allocated in MCG Discard ra-PreambleIndex and ra- Stopongoing scheduling request PRACH-maskIndex allocated in SCG procedure ina PCell Stop ongoing scheduling request Stop ongoing buffer statusreporting procedure in a pSCell procedure at P-MAC entity Stop ongoingbuffer status reporting Stop ongoing power headroom reporting procedureat S-MAC entity procedure at P-MAC entity Stop ongoing power headroomreporting Flush soft buffers of HARQ processes of procedure at S-MACentity MCG serving cells Flush soft buffers of HARQ processes of Discardtemporary identifier (C-RNTI) SCG serving cells allocated in randomaccess procedure Discard temporary identifier (C-RNTI) allocated inrandom access procedure Discard identifier (C-RNTI) allocated for use inSCG

In Table 13, TimeAlignmentTimers, NDI, ra-PreambleIndex, andra-PRACH-MaskIndex comply with those specified in TS36.321.

The reason why the C-RNTI is maintained in resetting the P-MAC butdiscarded in resetting the S-MAC is because the current C-RNTI is usedfor resuming the P-MAC entity in the new cell when resetting the P-MACentity while such operation is not required when resetting the S-MACentity.

FIG. 17 is a flowchart illustrating an SCell release procedure of a UEaccording to an embodiment of the present disclosure.

Referring to FIG. 17, the SCell may be released according to theinstruction of the eNB or the autonomous determination of the UE. If itis determined to release an SCell of a UE, the eNB transmits to the UEthe RRC Connection Reestablishment message including SCellIndexinformation as the identifier of the cell to be released.

If the RRC connection procedure is triggered for the reason of RLF, theUE releases the configured SCells at the corresponding timing.

At operation 1705, an event requiring release of at least one SCelloccurs to the UE. As described above, this event is of receiving an RRCcontrol message fulfilling a certain condition or initiating the RRCconnection reestablishment procedure. The RRC connection reestablishmentprocedure complies with that specified at section 5.3.7 of 3GPPTS36.331.

At operation 1710, the UE determines whether the event is of receivingthe RRC Connection Reestablishment message including first informationor initiating the RRC Connection Reestablishment procedure and, if theevent is of receiving the RRC Connection Reestablishment messageincluding the first information, the procedure goes to operation 1715and, otherwise if the event is of initiating the RRC ConnectionReestablishment procedure, the procedure goes to operation 1725.

The first information is SCellToReleaseList including the indices of theSCells to be released.

At operation 1715, the UE identifies the SCells having the same SCellindices as the CellToReleaseList among the SCells configured to the UEcurrently and releases the corresponding cells. If an SCell is released,this indicates that the transceiver is reset to stop receiving the PDSCHand transmitting PUSCH through the corresponding SCell.

The UE determines whether any SCG is configured (or DC is configured ortwo cell groups are configured) operation 1720 and, if no SCG isconfigured, releases all SCells configured at that time point atoperation 1725 and ends the procedure.

If any SCG is configured, the UE releases the pSCell as well as allSCells configured at the time point at operation 1730. If the RRCConnection Reestablishment procedure is initiated, this indicates thatan issue has occurred in the current RRC connection and thus it ispreferred to stop uplink transmission immediately. Accordingly, it ispreferred to release the pSCell too.

FIG. 18 is a flowchart illustrating an SCell management procedure of aUE in an RLF situation according to an embodiment of the presentdisclosure.

Referring to FIG. 18, the UE detects RLF at operation 1805. For example,if T310 or T310 s time expires, it is determined that RLF occurs.

The UE determines whether the RLF is SCG-RLF or MCG-RLF at operation1810. The SCG-RLF occurs due to the issue in a SCG serving cell,particularly when a state in which the channel condition of the pSCellis below a certain threshold lasts over a certain duration. The MCG-RLFoccurs due to the issue in a MCG serving cell, particularly when a statein which the channel condition of the PCell is below a certain thresholdlasts over a certain duration.

If the RLF is the SCG-RLF, the procedure goes to operation 1815 andotherwise if the RLF is the MCG-RLF, operation 1825.

At operation 1815, the UE stops uplink transmission in the SCG servingcells, i.e., SCells and pSCell included in the SCG. At this time, the UEmaintains the SCG serving cells and pSCell rather than releasing them.This is because the current configuration may be referenced in SCGserving reconfiguration afterward.

The UE generates a control message called ‘UE failure indication’ andtransmits to the eNB the UE failure indication message through the MCGserving cells at operation 1820 and ends the procedure. This controlmessage may include SCG-RLF reporting information and measurementinformation about the neighboring cells of the SCG serving cellfrequency.

At operation 1825, the UE releases the SCG serving cells, i.e., SCellsand pSCell included in the SCG. This is because if the MCG-RLF the UE islikely to reestablish the RRC connection with a new eNB and thus it isunlikely to reuse the current SCell and pSCell configuration.

The UE initiates the cell reselection procedure (see TS 36.304) to findthe cell suitable for RRC connection reestablishment. If a new cell isselected, the UE transmits to the newly selected serving cell an RRCConnection Reestablishment Request message at operation 1830.

An embodiment of the present disclosure proposes an in-deviceinterference resolution procedure of the UE.

In the case that multiple communication technologies (e.g., a cellularnetwork technology (LTE/UMTS), a Wireless Local Area Network (WLAN),Bluetooth, and a GNSS/GPS) coexist in an UE, one communicationtechnology-based transmission may interfere to another communicationtechnology-based reception and, this is called in-device interference.

In order to mitigate the in-device interference, when the in-deviceinterference occurs, the UE reports the in-device interference to theeNB, and the eNB takes a measure for canceling the in-deviceinterference based on the report from the UE, e.g., handover of the UEto another frequency.

An embodiment of the present disclosure proposes a method for addressingthe issue of reception failure of the location signal, such as a GlobalNavigation Satellite System (GNSS) signal, due to the in-deviceinterference.

If in-device interference occurs, the UE determines whether thein-device interference is that the LTE signal transmission interferesthe GNSS signal reception or that the LTE signal reception is interferedby other communication technology signal transmission and transmits tothe eNB an in-device interference report control message which includesan indicator of the LTE uplink frequency interfering the GNSS signalreception for the former case or an indicator of the LTE downlinkfrequency interfered by other communication technology signaltransmission for the latter case. At this time, the downlink frequencyis indicated explicitly while the uplink frequency is analogized basedon the relationship with the downlink frequency. The downlink frequencyalso may be indicated explicitly using a measurement target identifierwhile the uplink frequency is indicated using EARFCN.

FIG. 19 is a signal flow diagram illustrating an in-device interferencecontrol procedure of a UE according to an embodiment of the presentdisclosure.

Referring to FIG. 19, the UE receives a control message (e.g., an RRCConnection Reconfiguration message) for configuring of transmitting (ornot) the In-Device Coexistence Indication control message from the eNBat operation 1905. The In-Device Coexistence Indication control messageis the control message for reporting occurrence of in-deviceinterference, and the eNB configures the In-Device CoexistenceIndication message transmission to part of UEs in the RRC ConnectionReconfiguration procedure to prevent the control message from occurringtoo much or too frequently. The eNB may notify the UE of the In-DeviceCoexistence Indication message transmission availability using 1-bitinformation included in the RRC Connection Reconfiguration message.

The UE receives a control message for configuring measurement objectfrom the eNB at operation 1910. The control message may be the RRCConnection Reconfiguration message. The measurement object is LTE/E-UTRAfrequency to be measured by the UE, and the eNB configures anappropriate measurement object based on the UE capability, cell loadstatus, UE mobility status, and the like. It is also possible toconfigure multiple measurement objects to the UE. The eNB informs the UEof a measurement object frequency identifier (16-bit E-UTRA AbsoluteRadio Frequency Channel Number (EARFCN) (see TS 36.101) and a 5-bitMeasurement Object Identifier (ID).

Operations 1905 and 1910 may be performed with the same control messageor different control messages. Operations 1905 and 1910 may be changedin order.

The UE determines whether any in-device coexistence issue occurs atoperation 1913 and, if so, the procedure goes to operation 1915. At thistime, the UE determines the downlink and uplink frequencies fulfillingcertain conditions to determine whether the in-device coexistence issue.

At operation 1915, the UE determines whether the in-device coexistencereport message transmission is allowed. If the in-device coexistencereport message transmission is allowed, the procedure goes to operation1920 and, otherwise, waits until the in-device coexistence reportmessage transmission is allowed by going back to operation 1913. If thecurrent state corresponds one of the following situations, the UEdetermines that the in-device coexistence report message transmission isallowed.

-   -   In-device coexistence issue occurs on at least one LTE frequency        or is ongoing, and no in-device coexistence report control        message is transmitted yet since the in-device coexistence        report control message transmission has been configured.    -   In-device coexistence (hereinafter, referred to as IDC) problem        occurs on at least one LTE frequency or is ongoing, and the        frequency on which the IDC issue has occurred is changed        although the IDC report control message has been transmitted.

The UE determines whether the IDC issue has occurred on a downlinkfrequency or uplink frequency at operation 1920 and, if the IDC issuehas occurred on the downlink frequency, the procedure goes to operation1925 and, otherwise if the IDC issue has occurred on the uplinkfrequency, operation 1930.

At operation 1925, the UE transmits to the eNB an IDC report controlmessage including the first information indicating the downlink on whichthe IDC issue has occurred.

At operation 1930, the UE the eNB the IDC report control messageincluding the second information indicating the uplink on which the IDCissue has occurred.

If the IDC issue occurs on the downlink frequency, this indicates thatat least one of the LTE downlink frequencies configured as themeasurement objects is affected by the in-device interference. Such anIDC issue may be exemplified by a situation in which the received signalquality on the downlink frequency is degraded to the extent below acertain threshold by the in-device interference and this state lastsover a certain duration.

If the IDC issue occurs on the uplink frequency, this indicates that theuplink transmission performed on one or more LTE uplink frequenciesgives a bad effect to the receipt of an essential signal for locationmeasurement, such as a GNSS, a GPS signal, and the like. Such an IDCissue may be exemplified by a situation in which the UE fails receivingthe essential signal for location measurement over a certain timeperiod.

In the current standard, a plurality of LTE frequencies is defined. Ifthe UE has to determine all of the LTE frequencies to determine whetherthe IDC issue occurs, this is very burdensome to the UE.

In an embodiment of the present disclosure, the UE monitors thefollowing LTE frequencies for determining IDC issue occurrence.

-   -   DL frequencies configured as measurement objects, and    -   UL frequencies of current serving cell of UE.

The serving cells of the UE include a PCell which is configured withuplink and SCell(s) which is configured with uplink. Accordingly, the UEmonitors the uplink of the PCell and uplinks of the SCells that areconfigured with uplink for detecting IDC issue.

The first information indicating the downlink frequency on which the IDCissue has occurred is the identifier of the downlink frequency as themeasurement object. For example, the UE transmits to the eNB a controlmessage including the measurement object identifier indicating thedownlink frequency on which IDC issue has occurred at operation 1925. Atthis time, the UE may transmit the information notifying that the IDCissue relates to LTE reception too. This information may notify whetherthe in-device interference affects the E-UTRA, other communicationtechnology operation, or both of them. At operation 1925, the UE maytransmit the information notifying the in-device interference affectsthe E-UTRA, i.e., the E-UTRA is the victim of the in-deviceinterference.

The second information indicating the uplink frequency on which the IDCissue has occurred is the EARFCN indicating the uplink frequency ormeasurement object identifier configured to the downlink frequencyrelated to the uplink frequency. If an uplink frequency is associatedwith a downlink frequency, this indicates that the downlink signalreceived through the downlink frequency has a relationship ofcontrolling or influencing the uplink signal transmitted through theuplink frequency. For example, the uplink transmission resource foruplink transmission associated with the downlink may be allocated. Inuplink transmission, the pathloss of the associated downlink may beconsidered in configuring the transmit power. In the case of the PCell,the relationship is notified through system information (SystemInformation Block 2) and, in the case of the SCell, through an RRCcontrol message (RRC Connection Reconfiguration message).

The UE transmits to the eNB the IDC report message including EARFCNindicating the uplink frequency on which the IDC issue has occurredexplicitly or a measurement object identifier indicating the uplinkfrequency on which the IDC issue has occurred implicitly. The controlmessage also may include the information notifying of the influence ofthe in-device interference to other communication technology operation,e.g., a GPS operation, other than E-UTRA.

FIG. 11 is a block diagram illustrating a configuration of a UEaccording to an embodiment of the present disclosure.

Referring to FIG. 11, the UE according to an embodiment of the presentdisclosure includes a transceiver 1105, a controller 1110, amultiplexer/demultiplexer 1115, a control message processor 1130, andupper layer processors 1120 and 1125.

The transceiver 1105 is responsible for receiving data and a controlsignal through a downlink channel of the serving cell and transmittingdata and control signals through an uplink channel. In the case that aplurality of serving cells is configured, the transceiver 1105 transmitsand receives data and control signals through the plural serving cells.The transceiver 1105 may include an RF Circuit/Front End of whichoperation frequency is configured under the control of the controller1110.

The multiplexer/demultiplexer 1115 is responsible for multiplexing datagenerated by the upper layer processors 1120 and 1125 and the controlmessage processor 1130 or demultiplexing data received by thetransceiver 1105 to deliver the demultiplexed data to the upper layerprocessors 1120 and 1125 and the control message processor 1435.

The control message processor 1130 is an RRC layer entity for processingthe control message received from the eNB to take action. For example,the control message processor 1130 receives RRC control message andtransfers the SCell configuration information and transmit power controlinformation to the controller 1110.

The upper layer processor 1120 and 1125 is established per service. Theupper layer processors 1120 and 1125 process the data generated in theuser service, such as File Transfer Protocol (FPT), Voice over InternetProtocol (VoIP), and the like, and transfers the processed data to themultiplexer/demultiplexer 1115 or processes the data from themultiplexer/demultiplexer 1115 and delivers the processed data to theupper layer service applications.

The control unit 1110 determines the scheduling command, e.g., uplinkgrants, received through the transceiver 1105 and controls thetransceiver 1105 and the multiplexer/demultiplexer 1115 to performuplink transmission with appropriate transmission resource at anappropriate timing. The controller 1110 also controls the SCellconfiguration procedure and the transmit power control procedure. Forexample, the control unit 1110 controls the UE operations described withreference to FIGS. 3 to 10. Although the controller 1110 and thetransceiver 1105 are depicted as separated components in FIG. 11, partof the controller 1110 may be implemented in the transceiver 1105. Moreparticularly, the transmit power adjustment may be controlled by aseparate control mode included in the transceiver 1105.

FIG. 12 is a block diagram illustrating a configuration of an eNBaccording to an embodiment of the present disclosure.

Referring to FIG. 12, the eNB includes a transceiver 1205, a controller1210, a multiplexer/demultiplexer 1220, a control message processor1235, upper layer processors 1225 and 1230, and a scheduler 1215.

The transceiver 1205 is responsible for transmitting data and a controlsignal through a downlink channel and receiving data and control signalsthrough an uplink channel. In the case that a plurality of carriers isconfigured, the transceiver 1205 transmits and receives data and controlsignals through the plural carriers.

The multiplexer/demultiplexer 1220 is responsible for multiplexing datagenerated by the upper layer processors 1225 and 1230 and the controlmessage processor 1235 or demultiplexing data received by thetransceiver 1205 to deliver the demultiplexed data to the upper layerprocessors 1225 and 1230, the control message processor 1235, and thecontroller 1210. The control message processor 1235 processes thecontrol message transmitted by the UE to take action or generates acontrol message addressed to the UE to the lower layer.

The upper layer processor 1225 (or 1230) is established per service,processes the data to be transmitted to the S-GW or another eNB into RLCPDU and transfers the RLC PDU to the multiplexer/demultiplexer 1220, andprocesses the RLC PDU from the multiplexer/demultiplexer 1220 into PDCPSDU to be transmitted to the S-GW or another eNB.

The scheduler 1215 allocates transmission resource to the UE at anappropriate timing based on the buffer state and channel condition ofthe UE and processes the signal transmitted form the UE or to betransmitted to the UE through the transceiver 1205.

The controller 1210 controls the SCell configuration procedure and thetransit power adjustment procedure. The controller 1210 controls the eNBoperations described with reference to FIGS. 3 to 10.

The following terms that are used in embodiments of the presentdisclosure comply with the definitions specified in 3GPP TS 36.211,36.212, and 36.213.

-   -   PUCCH, CSI, CQI, PUSCH, PDSCH, HARQ feedback, Uplink grant,        Downlink Assignment, and Uplink Control information (UCI).

As described above, the multicarrier-based data transmission method andapparatus of the present disclosure is advantageous in terms ofincreasing the data rate of the terminal through inter-eNB carrieraggregation.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method by a terminal which is capable ofcommunicating with a master base station and a secondary base station ina wireless communication system, the method comprising: receiving, fromthe master base station, a first control message including a firstcell-radio network temporary identifier (C-RNTI) for a master cell group(MCG) associated with the master base station and a first RNTI for apower control of a physical uplink channel for the MCG; receiving, fromthe master base station, a second control message including a secondC-RNTI for a secondary cell group (SCG) associated with the secondarybase station and a second RNTI for a power control of a physical uplinkchannel for the SCG; monitoring a cell of the MCG based on the firstC-RNTI for the MCG; monitoring a cell of the SCG based on the secondC-RNTI for the SCG; monitoring a primary cell of the MCG based on thefirst RNTI for the power control of the physical uplink channel for theMCG; and monitoring a primary cell of the SCG based on the second RNTIfor the power control of the physical uplink channel for the SCG.